1. Not enough energy to be regenerated off the rear wheel of a lightweight motorcycle. Most braking force is applied to the front wheel of a motorcycle (some 70%) – and applying braking force to the rear wheel is a tricky deal without knowing traction conditions. All of this at the maximum benefit of much less than 10% increase in range.
2. Regen turns your motor into a generator – which means it’s working when it might otherwise be resting. This adds heat to the motor and can reduce the service life of the motor by increasing the duty cycle.
3. Control – regen is a variable parameter and probably requires an additional hand control to be done properly. Vectrix did this by twisting the throttle forward, which was elegant but also presented problems. New riders were slowing only with regen and failed to learn how to apply the true mechanical brakes properly when they needed to stop fast!
4. Range – in most cases, you’ll experience greater range by “free wheeling” and coasting with no regen than you would if regen kicked in when you let off the throttle.

Did the Brammo ever have regen? (edit: Yes, it did, described as "sluggish" in one review) This was ca. 2009, so I know a lot of the opinions voiced by Brian that early on got, er, modified once the Empulse went into production. I know the Energica had regen but it all went through the VCU, and how you manage that is beyond my pay grade. I will say, though, it was a glorious experience. I felt fully in control, it was really seamlessly responsive.

I had a long chat with Rob Barber, the guy who rode the first Agni bike that won the TTXGP, and then Ohio State's rider on both the TTZero and Pikes, and he turns regen completely off. He prefers to control the front and rear with the throttle and brakes, and doesn't feel the need for any "engine braking" on top of that. In fact, he felt it was a distinct disadvantage. Of course, he rides a lot faster than most of us.

Sorry, not too much answering the direct question... but it's a slow day at work.

I concur with Brian's comments that Ted posted above. I have been riding Zero motorcycles for the past four years with an owner custom adjustable firmware program that allows you to select how much regen you want to have when coasting with the throttle closed and also when braking. I have experimented quite a bit and have determined to my satisfaction that the best arrangement for getting maximum mileage from the battery pack is to have no regen when coasting with the throttle closed and maximum regen (which is not all that strong anyway on Zeros) when the brakes are being used. Having strong regen on a motorcycle when the throttle is closed results in having to turn the power on and off to maintain a steady speed under any condition other than when traveling down a steep hill. Regen just isn't all it is cracked up to be when employed on a motorcycle. It works a lot better when used on a car - the heavier the better.

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I liked how my Brammo had the regen (and similarly the 2013 Zero I rode). They did what is called Neutral Braking (which is like off throttle, or engine braking). It works well with torque control. Push the throttle to where you want the torque to be, and it gives that torque. Less throttle and there's a deadband, where it just coasts. Let off the throttle and the neutral braking kicks in. I adjusted mine lower than stock, as I didn't like the aggressive regen in sport mode.

Also, there's two types of regen with these Sevcon (and Curtis) controllers. Neutral braking (like above) and a separate brake input. Both controllers have an analog input that can be used with another 0-5V signal (another throttle like PB6 hooked to a cable, or a hydraulic pressure sensor reading off the rear brake pressure). It can also be just a switch that goes on/off, piggybacking off of a brake light switch.

When I built my eVFR, and upgraded to the AC20, I was going to use both. I wanted off throttle set to about 5-10%, to gradually slow me down without brakes, and another brake pressure transducer (via banjo bolt connection) on the rear brake line for more brake when I wanted it, but based on the pressure (not on/off). So for me, I think I'd like less neutral braking, and the ability to control the brake input regen proportionally.

Hope that helps. I have a bit of experience adjusting both Sevcon and Curtis for my customers, so any questions, let me know.

Using a Sevcon Gen4 controller I had a left hand brake lever tied to a pressure transducer. This 5V signal was feed to the sevcon and applied variable regen. 150psi transducer powered by a little 12V to 5V linear regulator.

If I did it again Iíd use a higher pressure transducer for more resolution. It didnít feel like I was pulling hard enough for the amount of braking I was getting. Maybe a larger reservoir too. I just had a tube with a plug on the end. The initial impulse of the regen was abrupt. I think most likely due to the chain slack switching from tension on the top to the bottom. A tighter chain usually made it feel worse.

One thing I did notice is it would loosen/stretch my chain quicker. I did run a 420 chain so that could be contributing.

It maxed out at about 6kW peak from where I had it set and only broke traction maybe once using it. It was quite useful for leisurely riding and hypermiling but I never got comfortable enough with it to use it second nature.

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My system does not have regen, but that doesn't mean I haven't thought about it.

The idea I decided I'm not be interested in is clutch lever for regen. Although it would seem fairly intuitive (you often pull the clutch when braking) you also often don't pull the clutch when using the rear brake.
I'm a big fan of the value of coasting, so I think I would prefer variable regen through a transducer on the rear brake pedal, with the second 50% of the pedal actually actuating the mechanical brake.

I have wondered, depending on motor and controller setup, and regen power, whether one could completley replace the rear brake with regen. My ICE bike braking power is about 90-10 front-back anyway.

when I saw that you posted that, I had to go check that other thread to see if it had gone off the rails because I posted this:

Originally Posted by T Rush

...
one of the things I was researching was regenerative motor braking analog control using the old clutch lever and cable...

here is one of the links to his High-End No Compromise EV car using a TPS and rigid arm linkage to the shifter(instead of clutch cable) http://www.metricmind.com/audi/10-shifter.htm
[before anyone goes nuts on if engine braking of any kind is good to do on a motorcycle, or if regen is worth it or not....I'm not a believer in any of that; and basically want to keep the clutch lever mainly as a way to mount the left mirror lol, and have it matching the looks of the right side bar, also so when people ask if it has "regen" I can point at the repurposed clutch lever and they can say 'oh cool'...seriously thats about it, and worth the time and maybe $30]
...

phew, it hadn't ....and the other things people posted about the regen functions of throttle seemed pertinent
[btw, just wanted to carry that quote over here so anyone can follow the link and see MetricMind's kinda cool experiences and setups for regen....pretty informative breakdown of the different control methods if you haven't read his stuff]

but I'm glad you made this new thread on the subject because I've been reading on this lately, and wanted to hear other people's thoughts
...I'd also come across this in Ted's blog that I liked(well, I actually like and appreciate all his stuff on there and here, and have learned a lot from it)
[I'm gonna bold a few things I found the most important]

1. Not enough energy to be regenerated off the rear wheel of a lightweight motorcycle. Most braking force is applied to the front wheel of a motorcycle (some 70%) – and applying braking force to the rear wheel is a tricky deal without knowing traction conditions. All of this at the maximum benefit of much less than 10% increase in range.
2. Regen turns your motor into a generator – which means it’s working when it might otherwise be resting. This adds heat to the motor and can reduce the service life of the motor by increasing the duty cycle.
3. Control – regen is a variable parameter and probably requires an additional hand control to be done properly. Vectrix did this by twisting the throttle forward, which was elegant but also presented problems. New riders were slowing only with regen and failed to learn how to apply the true mechanical brakes properly when they needed to stop fast!
4. Range – in most cases, you’ll experience greater range by “free wheeling” and coasting with no regen than you would if regen kicked in when you let off the throttle.

...

on lighter sport type bikes I just really hardly ever use much rear braking at all, where on a FWD EV car I'm sure regen can be more of a benefit.....maybe on a cruiser/chopper style of bike if converted to EV(but you just don't see many of those) where riders use more engine and rear mechanical braking(which is strange to do if you have ever owned or riden one) regen use might come more into play? maybe idk

but I think thats very interesting that riders would become accustomed to regen, and then have problems with normal braking when they needed it

came across this awhile ago...its a Lotus Evora with a Tesla motor in it...but at the track they only had level 2 charging, so they ended up towing it with the regen on(not that doing this would be safe or easy with an eMotorbike, but just saying regen could be good stuff for last resort charging) but they were able to fast charge at 50kW with regen vs the 3kW rate the onboard charger could have given them https://www.youtube.com/watch?v=yyyqqPSIwqA

Last edited by T Rush; 06 April 2018 at 0526.
Reason: added the link to Ted's blog incase anyone wanted to find what he was quoting and read more

I'm glad I checked in today.... I've been wondering about this also, as I have never ridden a bike with regen, and my new system will have the ability. So, now I'm more confused about it then before! LOL

Travis, any experience with the Domino throttle regen set up? Do you sell Dominos? I have a Magura